Method and apparatus for reversing a tubular bag

Abstract

An apparatus for reversing a tubular bag for internally lining a utility pipe installed underground, which includes a container for defining a closed space and containing a liquid body, constructed such that an amount of a liquid body therein has first and second level surfaces, the first partially defining the closed space and the second being exposed to atmospheric air; a compressor to supply compressed air to the closed space; and the tubular bag to be reversed. The tubular bag is primarily arranged in a manner such that it penetrates through the liquid body passing the first and second level surfaces and also penetrates through the closed space, with one end portion of the bag placed in atmospheric air and the other end portion thereof reversed and fixed, and some of the reversed portion partially defining the closed space so that when the pressure in the closed space is increased that portion of the tubular bag which is defining the closed space is forced to inflate and be reversed further. Compressed air is supplied to the closed space by a compressor, whereupon the tubular bag is inflated and be reversed further. The bag itself can be used to contain the liquid body without employing a container.

What is claimed is: 
     
       1. A method for reversing an elongate tubular element into a pipe to line the pipe, comprising the steps of: providing a predetermined quantity of a liquid into a portion of the elongate tubular element defined solely within an open reversed end portion of the tubular element disposed to be in a generally N shape as viewed from a side, in a manner such that said liquid has first and second level surfaces, the first level surface partially defining a closed space and the second level surface being exposed to atmospheric air;   arranging the tubular element such that it extends from said open end portion through said liquid via said first and second level surfaces and also penetrates through said closed space, with the reversed end portion held fixed, whereby said reversed portion partially defines a variable volume of said closed space; and   increasing a pressure in the closed space by supplying compressed air thereto from a compressed air supply source, to thereby pressurize said reversed portion of the tubular element which is defining said closed space to inflate the tubular element to extend and further reverse more of the tubular element,   wherein the liquid-containing portion of the tubular element is disposed below an end thereof open to the atmosphere and passes over a first support at a first location and then over a second support at a second location higher than said first location.   
     
     
       2. The method according to claim 1, wherein: most of the length of the tubular element is initially located in an unreversed form outside the closed space and is forcibly pulled by pressure of the compressed air longitudinally through the liquid and into the closed space filled with compressed air as the tubular element is being reversed.   
     
     
       3. An apparatus for reversing an elongate tubular element into a pipe to line a pipe, comprising: means for holding open to the atmosphere a reversed first end of the tubular element, with a reversed first length of the tubular element extending therebelow and supported to have a shape generally like the letter "N" when viewed from a side, a further unreversed length of the tubular element being extended within said first length to an aversion point;   first and second means for supporting said reversed first length of the tubular element to maintain said generally N-shape thereof during reversing, said first means supporting said tubular element at a location lower than a location at which said second means supports said tubular element;   a quantity of a liquid of predetermined specific gravity, held solely in said reversed first length of the tubular element in such a manner as to have a first liquid surface exposed to the atmosphere and to have a second liquid surface located at a level between said locations of support by said first and second shape-maintaining means to define and seal a closed space inside a portion of said reversed first length extending to said eversion point; and   means for providing compressed air to said closed space to pressurize the same so that said first liquid surface is raised correspondingly higher than said second liquid surface, whereby the pressure within said closed space causes a further length of said unreversed tubular element to move inside said reversed first length through said liquid and to evert and become reversed,   said tubular element providing the sole containment means for said liquid during reversing.